I do not claim to know anything about patent law. So, i would appreciate some direction. If a patent is filed and the original term of the patent is 20 yrs, according to my research, there is no extension of the protection period. Is that right? Why would anyone file a patent if you only get 20 yrs of patent protection? What am i missing here?

Patents usually only have a shelf life of 20 yrs. If you change the patent application then you can obtain a patent under separate application. It takes a special act of Congress to renew an existing patent, so most patent holders must make the most of the standard 20 years during which they can hold a patent. According to the U.S. Patent and Trademark Office, or USPTO, in the case of some drug companies, the USPTO will renew an existing patent on a pharmaceutical drug that has lost part of the patent period to the FDA approval process.

Patent protection only lasts 20 years (14 years for design patents) in the United States. After expiration of the term of the patent, the person holding the patent loses the right to exclude others from utilizing the invention, so that anyone can go ahead and make use of the invention without permission of the patent holder. Copyright protection lasts almost 100, depending on when it was filed. Trademark protection is forever, as long as you are using it.